Thermal conductivity of B-C-N and BN nanotubes

We have measured the temperature-dependent thermal conductivity ͑T͒ of boron-carbon-nitride ͑B-C-N͒ and boron nitride ͑BN͒ nanotube mats. The thermal conductivity of B-C-N nanotubes is phonon dominated and reflects dimensional effect below 70 K. We employ a new analysis method to estimate the intrinsic ͑T͒ of BN nanotubes converted from B-C-N nanotubes, and find that at room temperature ͑T͒ of a multiwalled BN nanotube is within 0.04-0.32 times that of a multiwalled carbon nanotube. The lower ͑T͒ of BN nanotubes than that of carbon nanotubes may be due to the enhanced isotope disorder effect in one dimension

A theoretical study of thermal conductivity in single-walled boron nitride nanotubes

We perform a theoretical investigation on the thermal conductivity of single-walled boron nitride nanotubes (SWBNT) using the kinetic theory. By fitting to the phonon spectrum of boron nitride sheet, we develop an efficient and stable Tersoff-derived interatomic potential which is suitable for the study of heat transport in sp2 structures. We work out the selection rules for the three-phonon process with the help of the helical quantum numbers $(\kappa, n)$ attributed to the symmetry group (line group) of the SWBNT. Our calculation shows that the thermal conductivity $\kappa_{\rm ph}$ diverges with length as $\kappa_{\rm ph}\propto L^{\beta}$ with exponentially decaying $\beta(T)\propto e^{-T/T_{c}}$, which results from the competition between boundary scattering and three-phonon scattering for flexure modes. We find that the two flexure modes of the SWBNT make dominant contribution to the thermal conductivity, because their zero frequency locates at $\kappa=\pm\alpha$ where $\alpha$ is the rotational angle of the screw symmetry in SWBNT.Comment: accepted by PR

The electronic properties of doped single walled carbon nanotubes and carbon nanotube sensors

We present ab initio calculations on the band structure and density of states of single wall semiconducting carbon nanotubes with high degrees (up to 25%) of B, Si and N substitution. The doping process consists of two phases: different carbon nanotubes (CNTs) for a constant doping rate and different doping rates for the zigzag (8, 0) carbon nanotube. We analyze the doping dependence of nanotubes on the doping rate and the nanotube type. Using these results, we select the zigzag (8, 0) carbon nanotube for toxic gas sensor calculation and obtain the total and partial densities of states for CNT (8, 0). We have demonstrated that the CNT (8, 0) can be used as toxic gas sensors for CO and NO molecules, and it can partially detect Cl$_2$ toxic molecules but cannot detect H$_2$S. To overcome these restrictions, we created the B and N doped CNT (8, 0) and obtained the total and partial density of states for these structures. We also showed that B and N doped CNT (8, 0) can be used as toxic gas sensors for such molecules as CO, NO, Cl$_2$ and H$_2$S.Comment: 12 pages, 13 figure

Thermal conductivity of the Toda lattice with conservative noise

We study the thermal conductivity of the one dimensional Toda lattice perturbed by a stochastic dynamics preserving energy and momentum. The strength of the stochastic noise is controlled by a parameter $\gamma$. We show that heat transport is anomalous, and that the thermal conductivity diverges with the length $n$ of the chain according to $\kappa(n) \sim n^\alpha$, with $0 < \alpha \leq 1/2$. In particular, the ballistic heat conduction of the unperturbed Toda chain is destroyed. Besides, the exponent $\alpha$ of the divergence depends on $\gamma$

Assessment of the Thermal Conductivity of BN-C Nanostructures

Chemical and structural diversity present in hexagonal boron nitride ((h-BN) and graphene hybrid nanostructures provide new avenues for tuning various properties for their technological applications. In this paper we investigate the variation of thermal conductivity ($\kappa$) of hybrid graphene/h-BN nanostructures: stripe superlattices and BN (graphene) dots embedded in graphene (BN) are investigated using equilibrium molecular dynamics. To simulate these systems, we have parameterized a Tersoff type interaction potential to reproduce the ab initio energetics of the B-C and N-C bonds for studying the various interfaces that emerge in these hybrid nanostructures. We demonstrate that both the details of the interface, including energetic stability and shape, as well as the spacing of the interfaces in the material exert strong control on the thermal conductivity of these systems. For stripe superlattices, we find that zigzag configured interfaces produce a higher $\kappa$ in the direction parallel to the interface than the armchair configuration, while the perpendicular conductivity is less prone to the details of the interface and is limited by the $\kappa$ of h-BN. Additionally, the embedded dot structures, having mixed zigzag and armchair interfaces, affects the thermal transport properties more strongly than superlattices. Though dot radius appears to have little effect on the magnitude of reduction, we find that dot concentration (50% yielding the greatest reduction) and composition (embedded graphene dots showing larger reduction that h-BN dot) have a significant effect